The present invention relates to a yarn break detector for spinning and weaving machines, More particularly, it relates to a device for detecting yarn break or stoppage of yarn run by monitoring the state of running of yarn in a spinning or weaving machine.
In the production of yarns or textile goods by use of a spinning or weaving machine or other textile machines, if there takes place an unexpected break on the spun out of fed yarn in the production process, the obtained products will become defective. In order to cope with such trouble, it is required to incorporate a suitable countermeasure such as providing a means for issuing an alarm or stopping the machine upon occurrence of yarn break.
Various types of yarn break detecting means have been proposed and used, which include the following: microswitch system in which a microswitch is connected to an actuator so that said microswitch will be opened or closed according to the presence or absence of yarn tension to thereby detect the yarn break; photoelectric system in which light is projected to the yarn to detect the yarn break, should it occur, by the variation of its projection; electrostatic capacity system in which the yarn is let run between two pieces of electrode and the variation of electrostatic capacity between the two electrodes is monitored to detect any yarn break; electric charge detection system in which the variation of electric charges on the yarn is monitored to detect the yarn break.
Any of these known systems, however, has its own merits and demerits. For instance, the microswitch system is advantageous in terms of cost, but this system has the problems that a detecting element must be always mechanically kept in contact with the yarn, and that the operation of the system is not always reliable.
The photoelectric and electrostatic capacity, systems are capable of performing detection in a non-contacted state with the yarn and also relatively reliable in their operations, but they are both costly in adaptation. Also, the photoelectric system has the necessity of regulating the yarn path, while the electrostatic capacity system has the problem of complicated circuit structure because of the use of high frequencies.
The electric charge detection system is susceptible to the influence of the electric field induced from the outside and therefore bad in the signal/noise ratio (S/N ratio). Also, since this system necessitate a shield plate for shutting off the induced noise, the scope of use thereof is limited.
In view of these problems of the prior art systems, the present inventors have made more extensive studies and succeeded in achieving the present invention.